Alternating-current telegraph system



J. P. FERRITER ET AL ALTERNATING CURRENT TELEGRAPH SYSTEM June 7, 1927. 1,631,676

Filed Sept. 5, 1925 2 Sheets-Sheet l gwvcnfom 1631676 June 1927' J. P. FERRITER ET AL ALTERNATING CURRENT TELEGRAPH SYSTEM 2 Sheets-Shet 2 Filed Sept 5, 1925 WNR m) NMNI Patented June 7, 1927.

' UNITED STATES 1,631,676 PATENT-'0 OFFICE.

JOHN P. FERRITER, OF OGEANPORT, AND WESLEY T. GUEST, 0F EATONTOWN, JERSEY.

ALTERNATING-CURRENT TELEGRAPH SYSTEM.

Application filed September 3, 1925. Serial No. 54,290.

The general objectof this invention is to provide a new and efiicient method of utilizing alternating current for telegraph purposes.

A more specific object is to provide a means of utilizing the positive half cycles of the transmitted alternating current to oper ate a telegraph relay at the distant station and the'negative half cycles to operate a second telegraph relay at the distant station, thus providing two independent circuits on the same wire and with the same alternating current power.

With the foregoing and other objects in I view, the invention consists in the combina tion and arrangement of parts hereinafter set forth, certain embodiments thereof being illustrated in the accompanying drawings, in which:

Figure 1 is a diagrammatical showing of one form of the invention employing an alternating current.

Figure 2 is a digrannnatical showing of a modified form'of the invention employing a direct current.

In Figure 1, AC represents a source of alternating current, which may be of any desired audible frequency and preferably of a sinusoidal form. T, T,, T. ,,T,, and T, rep

resent transformers.

Terminal 1 of secondary winding S of transformer T is connected to the grid G of a three electrode power vacuum'tube V and terminal 2 of secondary winding of transformer T is connected to the filament of the same vacuum tube and to the lever of key K. in parallel. Terminal 2 of secondary winding S, of transformer T is connected to the grid G, of power vacuum tube V, and terminal 1 of the secondary winding of transformer T is connected to the filament of vacuum tube V,. Terminal 1 of secondary windings S, of transformer T is connected to the back contacts of keys K and K, in parallel, and terminal 2 of the same secondary winding is connected to the front contacts of keys Kand K and to the earth E in parallel. Plate PLl of tube V is connected to the lever of key K Plate PL of vacuum tube V and the filament of'vacuum tube V, are connected in parallel to the junction point 1 of equal resistance arms R and R each of which may have a value of from 500 to 1200 ohms. Terminal 2 of arm value to the resistance and capacity of the line and the associated apparatus at the distant' terminal, thus providing for duplex operation in a manner well known. The

artificial line is connected to the earth at E lVhat has been described constitutes the transmitting apparatus and source of power. The receiving apparatus is bridged across terminals 2 and 3 of the bridge arms R and 1%,, as is usual in bridge duplexes. Grid G of vacuum tube V, and the filament of vacuum tube V are connected in parallel to the line at its junction 2 with resistance R. Grid G, of vacuum tube V and the filament of vacuum tube V are connected in parallel to the artificial line at its junction 3 with resistance 1%,. Plate PL of vacuum tube V is connected in series with relay BL, secondary S of transformer T and the filament of the same vacuum tube. In a similar manner, plate PL of vacuum tube V, is con nected in series with relay RL,, secondary S of transformer T and the filament of vacuum tube V3. The primary windings of transformers T4 and T3 are supplied with alternating current from the power leads AC1, which may be identical with power leads AC.

The arrangement of apparatus we have de scribed, when connected by a suitable wire line to a similar arrangement of apparatus at a distant terminal, constitutes a means of transmitting four messages over a wire simultaneously, two in each direction. It may be operated manually or automatically. \Ve will describe its operation manually, by means of keys and reading sounders.

Figure 1 represents a telegraph duplex installation. By this we mean that, when a proper balance is obtained by adjusting AL and CN, signals originating at the home station will not actuate the receiving instruments at the home station, but will actuate the receiving instruments at the distant terminal of the line. lVith a proper balance of the artificial line at the distant station, the signals originating at the distant station will not affect the receiving instruments at that station. In this way, transmission of signals may be accomplished in both direc to operate a second receiving relay, thus virtually providing for the passage of two signals in each direction at the same time and, in so doing, We actually double the message carrying capacity of an ordinary duplexed telegraph circuit. This is acconr pflished as follows We connect a suitable source of alternating current at All, Figure 1. This may be of any desired audible frequency. In practice, we find'that a sixty cycle alternating c'urrentis suitable for manual operation and for single channel or two channel multiplex printing circuits. f A higher frequency is desirable Where more than two multiplex channels are operated.

ive will assume that keys K and K are both'resting on their back contacts. "Vith alternating current passing through the primary windings of transformers 'i, T and T a current will be induced in their corresponding secondary windings. It will be noted that tubes-V and V? are reversed with respect to each other and, as current can pass through a vacuum tube only when the plate is positivewith respect to the filament, a current passing through secondaries S and S will'cau'se only one tube to operate, depending upon the direction of current through thesecondaries. For example, a half cyclewhich would impress a negative potential upon grid G would cause grid G to 'become positive, and a half'cycle which would make G negative'would make G positive. In this way, one tube would operate during a positive half cycle and the Other duringa negative half cycle. It will be noted that the current induced in the secondary'S of transformer T is always in phase with the current induced in secondar'i'es S and'S so thatit is always flowing in the proper direction to provide current for the'plate circuits of tubes V and V at the instant either tube is operative. With this explanation, it will be seen that with keys K "and, K resting on their back contacts when grid G ismade positive by ahalf cycle through S,-a negative current will flow from E, through S the back contact of K, through tube V, from filament to plate PL andto junction point 1 of R and R where it divides, onehalf going through the artificial line to the'ear'th and the other half going over the line to the distant station and to earth. On the other hand, the next half cycle, which is in the opposite direction, will cause grid G of tube V to become positive and a positive current will flow from earth it, through S, back contact of key K through PLl tot'fi'lainentof'V ,'to junction .1301111; 1 of R and R where it divides, as d1d the previous half cycle. In this manner it will be seen thatywhen-one key is open, positive pulses are transmitted and, when the other key 'isop'ened, negative pulses are transmitted. lV hen both keys areopen, positive and negative pulses follow each other in regular succession. WVhen key K isclosed on its front contact, it has theefi'ect of connecting the plate circuit of tube V to the earth E, so that no current flows through 'it from transformer '.l.1, thus makingtubev inoperative. Similarly, closing K1 on its front contact connects the plate circuit of tube V to earth at E and makes tube'V in operative. In this manner, when both keys. are closed,'no current flows overthe line.

At the distant station, the signals are received follows:

When both keys are closed on their front contacts at the transmitting station and therefore no current is received at the receiving station, there isne current flowing through the coils of relays RL andRL and their armatures are held against the back contacts by retra'ctile springs. This will operate sounder-s SN and 'sN WVhen'key K ou its back contact at thet'ransieo pulsescause the armature'of r'elayRIi 'to vibrate and leave its back contact, which causes sounder SN to open. When key'KF is resting on its back contact at the transmitting station, it causes a succession 'of' positive pulses to reach the receiving station. These' make the 1 grid G of tube V positivew'ith respect to its filament and cause'relay contact RD and sounder'SN to open. Itwill be seen that there'are virtually two independent duplex circuit-s, one operating on the'positive and the other on the'negative half cyclesof an alternating'current.

While we have shown how we use alternating current in the plate circuits of the transmitting and receiving tubes, it'will be readily seen that the same alternatingcurrent can be used to heat the filaments of the trans mitting tubes. Thev alternating current supply for the plate circuit of the receiving tubes must be of the same frequency as the incoming 'current'or it must be appreciably F similarly with respect to battery B and key K One advantage of our system of alternating current telegraphy is that, by the use of filters, several different telegraph circuits may be operated over one wire. A second advanta e is that, in an alternating current telegraph circuit, vacuum tube repeaters may be used. We describe a suitable vacuum tube repeater for this purpose in an other patent application. A third advantage of our system of alternating current telegraphy is that it is secret.

What we claim is:

l. A system of telegraphy comprising a source of alternating current, means for utilizing the positive half-cycles of said current to operate a telegraph circuit and the negative half-cycles to operate a second telegraph circuit, said means comprising a pair of transmitting tubes, a pair of transformers each of which have their secondary indings connected to the grid of the adjacent tube, an intermediate transformer having its primary in parallel with said other transformers and said current source, keying means associated with said intermediate transformer for producing, through said secondary, negative pulses to affect a plate current in one of said tubes and positive pulses to affect plate current in said other tube.

2. A system of telegraphy comprising a source of alternating current, means for utilizing the positive half-cycles of said current to operate a telegraph circuit and the negative half-cycles to operate a second telegraph circuit, said means comprising a pair of transmitting tubes, a pair of transforn'iers' each of which have their secondary windings connected to the grid of the adjacenttube, an intermediate transformer having its primary in parallel with said other transformers and said current source, keying means associated, with said intermediate transformer for producing, through said secondary, negative pulses to affect a plate current in one of said tubes and positive pulses to affect plate current in said other tube, a receiving circuit including a distant line and an artificial line, a pair of tubes, a relay connected to the plate of each receiving tube and a transformer connected t each filament of said tubes.

v3. A system of telegraphy comprising a source of alternating current, means for utilizing the positive half-cycles of said current to operate a telegraph circuit and the negative half-cycles to operate a second telegraph circuit, said. means comprising a pair of. transmitting tubes, a pair of transformers each of which. have their secondary windings connected to the grid of the acent tube, an intermediate transformer having its primary in parallel with said other transformers and said current source, keying means associated with said intermediate transformer for producing, through said secondary, negative pulses to affect a plate current in one of said tubes and positive pulses to affect current in said other tube, a receivin circuit including a distant line and an artificial line, a pair of tubes, a relay connected to the plate of each receiving tube and a transformer connected to each filament of said tubes, an equal arm resistance bridge connected to said receiving and said transmitting circuit, said bridge being adapted to supply half of the transmitted current to said artificial line and thence to earth and the other half to said distant line.

In testimony whereof we aflix our signatures.

JOE-IN P. FERRITER. WESLEY T. GUEST. 

